Billy Crystal takes the stage to pay tribute to the late Robin Williams, shown on a large screen, during the 66th Primetime Emmy Awards in Los Angeles, California Aug. 25, 2014. Photo: Reuters/Mario Anzuoni

Robin Williams was suffering from “Lewy Body Dementia,” a neurodegenerative disease, which led to the 63-year-old comedian’s suicide, TMZ reported Tuesday, citing sources close to his family. The legendary entertainer was found dead on Aug. 11 at his home in northern California.

The report stated that Williams was struggling with the disease, which was the “key factor” that led to his untimely death. "Lewy Body Dementia" is a type of dementia closely linked with Parkinson’s disease. The disease reportedly disrupts the normal functioning of the human brain with deposits of abnormal proteins. Sources reportedly said that Williams' doctors had agreed that "Lewy Body Dementia" was a factor leading to his suicide.

"The central features of DLB include progressive cognitive decline, 'fluctuations' in alertness and attention, visual hallucinations, and parkinsonian motor symptoms, such as slowness of movement, difficulty walking, or rigidity," according to a definition of "dementia with Lewy bodies" from the National Institutes of Health.

"People may also suffer from depression. The symptoms of DLB are caused by the build-up of Lewy bodies – accumulated bits of alpha-synuclein protein — inside the nuclei of neurons in areas of the brain that control particular aspects of memory and motor control."

According to TMZ, people suffering from the disease are prone to side effects from the medication, while some also show signs of hallucination. Williams’ wife, Susan Schneider, reportedly told authorities that the “Mrs. Doubtfire” actor had been complaining about the medication he had been receiving.

An autopsy report released last week from the coroner in Marin County, California, ruled out the involvement of drugs and alcohol in his death.

In August, Schneider revealed in a statement that Williams had been struggling with depression and anxiety associated with the early stages of Parkinson’s disease. She added that he seemed to have been experiencing “a recent increase in paranoia.”

The coroner’s report said that Williams’ body was found by his assistant who entered the actor's locked room when he didn’t answer the door.